application of shotcrete in concrete rehabilitation and ... · application of shotcrete in concrete...

Application of Shotcrete in Concrete Rehabilitation and Repair

Works - Farah Hospital’s Extension Building Case Study

Author: Samer F. Altakroury

Position: Product Segments Leader at Don Construction Products (DCP) Co.

Mobile: +962 79 515 7718

Address: Wasfi Al-Tal St. P.O. Box 1117 Amman 11118 - Jordan

Tel.: +962 6 551 7019 Ext. 117

Fax: +962 6 551 7027

Email: [email protected]

Author: Mutaz S. Maroun

Position: Marketing Director at Don Construction Products (DCP) Co.

Mobile: +962 79 690 5607

Address: Wasfi Al-Tal St. P.O. Box 1117 Amman 11118 - Jordan

Tel.: +962 6 551 7019 Ext. 122

Fax: +962 6 551 7027

Email: [email protected]

mailto:[email protected]

mailto:[email protected]

i

Table of Content

List of Figures ............................................................................................................................................... ii

List of Annexes ............................................................................................................................................ iii

Abstract ......................................................................................................................................................... 1

Chapter One: Introduction ............................................................................................................................ 1

1.1: Project Overview ................................................................................................................................... 1

1.2: Introduction to Shotcrete ....................................................................................................................... 1

1.3: Task at Hand ......................................................................................................................................... 2

Chapter Two: Concrete Rehabilitation Methodology .................................................................................... 2

2.1: Onsite Assessment of Reinforced Concrete Condition .......................................................................... 3

2.2: Laboratory Testing ................................................................................................................................. 5

2.3: Recommendations and Conclusion for Repair Approach and Material ................................................. 6

Chapter Three: Development of the Repair Material .................................................................................... 6

3.1: Types of Shotcrete .................................................................................................................................. 6

3.2: Development of Shotcrete Product ........................................................................................................ 7

Chapter Four: Onsite Application of Shotcrete ............................................................................................. 8

4.1: Surface Preparation ................................................................................................................................ 8

4.2: Placement of Shotcrete .......................................................................................................................... 8

4.3: Post-Repairing Testing and Verification ................................................................................................. 9

Chapter Five: Conclusion ............................................................................................................................ 10

Acknowledgment ........................................................................................................................................ 10

References ................................................................................................................................................... 10

Annex A: Tables .......................................................................................................................................... 12

Annex B: Post-Repairing Testing Reports ................................................................................................. 23

ii

List of Figures

Figure 1: Farah hospital extension building after fire ................................................................................... 2

Figure 2: Depth of carbonation test ............................................................................................................... 4

Figure 3: Concrete coring in a column onsite ............................................................................................... 5

Figure 4: Prepacked shotcrete material onsite in preparation for the repair works ....................................... 7

Figure 5: Chipping of ribbed slabs and beams .............................................................................................. 8

Figure 6: Overhead application of shotcrete onsite ....................................................................................... 8

Figure 7: Elevator walls before and after the repairing works with shotcrete ............................................... 9

Figure 8: Installation of electro-mechanical works after repairing works .................................................... 9

Figure 9: Post-repairing verification by concrete coring ............................................................................ 10

iii

List of Annexes

Annex A: Tables .......................................................................................................................................... 12

Annex B: Post-Repairing Testing Report ................................................................................................... 23

1

Application of Shotcrete in Concrete Repair and Rehabilitation Works -

Farah Hospital’s Extension Building Case Study

Abstract

In August 2013, a major fire engulfed over 18,000 m2 of the 13-story expansion building of Farah Hospital (also

known as the Kilani Health Care Institute) in Amman, Jordan. As a result, major structural defections occurred on

the slabs, columns and walls over the majority of the building. In order to repair the damaged areas, shotcrete was

used to rehabilitate and repair the structural damage. Shotcrete is a pneumatically applied mortar or concrete on

prepared substrates. It is considered the most effective and economical method of concrete repair when concrete

deterioration has taken place over large vertical and overhead surfaces, which makes the traditional trowel applied

repairing mortar impractical and ineffective. This paper describes the methodology of the concrete repair and

rehabilitation work that was designed and implemented through a collaboration between Madi & Partners

Consulting Engineers (MPCE), Arab Center for Engineering Studies (ACES), Ayla Construction Chemicals (DCP

Jordan) and D. Bseiso & Partners Co.( B.E.M.C.O Engineering ) to put the project back onto its tracks and restore

the structural integrity of all defective elements. The process described includes the site assessment, the

requirements of repairing materials, placing and finishing as well as the onsite inspection and testing after

application.

Keywords: Shotcrete, Concrete repair, Rehabilitation, Fire

1. Introduction

1.1 Project Overview

Located in the center of Amman, Farah Hospital was established in 1978 and was made up of small clinics

specialized in obstetrics and gynecology. Since its establishment, the hospital has been expanding gradually with

notable milestones achieved. In 1985, a few years after the first successful In Vitro Fertilization (IVF) case in the

UK, Dr. Zaid Kilani, the founder of Farah Hospital, decided to introduce this technology to the country and region

and after several months of hard work Farah Hospital was the first medical institution to witness the birth of the first

IVF baby in Jordan on May 1st, 1987.

In 2014, another major milestone was reached in Farah Hospital that was the construction of a major extension to

the original hospital building. However, this project faced some delays due to a huge fire that engulfed over 9 stories

of the 13-story extension building. The fire left the building with major structural defection and required

collaborative engineering work between different parties to put the project back onto its track and repair what was

damaged.

1.2 Introduction to Shotcrete

Shotcrete, in the broadest sense, refers to a pneumatically applied mortar or concrete on previously prepared

surfaces. It is considered one of the most effective methods, in terms of cost, quality and productivity to restore the

structural integrity of defective reinforced concrete, increase the concrete cover over reinforcement bars or for both

of these applications.

Shotcrete can be applied using two different methods of application, which are the dry-mix process and wet-mix

process. The dry-mix process is the process in which the cementitious material and aggregate are mixed in dry

condition (i.e. without the addition of water), then the mixture is delivered to the operated gun nozzle where a water

ring injects water into the mixture as it is being discharged from the nozzle. The wet-mix process on the other hand

is the process in which all components, including the mixing water, are mixed in the same manner of conventional

concrete, the mixture is fed to a concrete pump which pushes it through a hose onto the prepared surfaces. It is

usually the contractors who select the method that they are comfortable with and have the needed equipment for.

However, according to the Standard Practice of Shotcrete published by the US Army Corps of Engineers, the dry-

mix shotcrete process tends to have higher bond strength with the substrate. In addition, the dry-shotcrete process

results in longer pumping distance but it usually yields more rebound than the wet-mix shotcrete process.

2

1.3 Task at Hand

As mentioned earlier, Farah Hospital’s extension building (also known as the Kilani Health Care Institute) was

under construction when an unfortunate fire engulfed the fifth floor of the building on August 5th

, 2013. The flames

quickly spread throughout 9 stories of the building from the 2nd

floor up to the 10th

floor. As a result, significant

damage to the structural elements of these stories occurred. In order to repair and complete the execution of the

building after the fire, it was necessary that several engineering parties come together to restore the integrity of the

structure and get the project back on track as fast as possible.

Since the defective area exceeded 18,000 m2 with variable repairing thicknesses, it was impractical to use traditional

hand applied repairing methods for the rehabilitation work. Shotcrete, on the other hand, represented a durable, high

performance and cost effective approach to be implemented.

The Arab Center of Engineering Studies (ACES) was entrusted by the project consultant, Madi & Partners

Consulting Engineers (MPCE), to assess the damaged reinforced concrete elements in the building. Based on this

assessment, Ayla Construction Chemicals (DCP Jordan) developed a special pre-bagged dry-mix proceed shotcrete

product that was designed to fulfill the project’s requirements. This product was applied by D. Bseiso & Partners Co.

(B.E.M.C.O Engineering), who completed all the required repair work within 90 days.

2. Concrete Rehabilitation Methodology

Fire is considered one of the four common causes of concrete deterioration other than mechanical, chemical and

physical causes. One of the most recognized references that addresses an integrated concrete repair methodology is

the “European Standard EN 1504: Products and systems for the protection and repair of concrete structures -

Definitions, requirements, quality control and evaluation of conformity - Part 9: General principles for the use of

products and systems.” According to this standard, a successful concrete repairing plan must go through certain steps

that include: (a) Assessing the condition of the concrete before repair, (b) Identifying the options and factors to be

considered prior to selecting the appropriate repair strategy, (c) Specifying the basic principles that shall be used to

repair the concrete structure and (d) Selecting the appropriate products and system that shall be used to fulfill the

technical requirements.

Figure 1. Farah Hospital’s extension building after fire (Photo credit: ACES)

Due to the sensitivity of the project and the extensive areas that were damaged, MPCE were keen to ensure the

accuracy of each step of the repair plan and since the right repairing method starts with proper site assessment,

ACES, a well-recognized third-party institution that provides specialized engineering services in geotechnical

engineering, material testing, environmental engineering and land and marine surveying, was entrusted to conduct a

full site examination to evaluate the effect of the fire on the structure and develop recommendations for

rehabilitation works. ACES’s scope of work consisted of:

• Collecting data about the site, defected structure and the surrounding natural and built environment.

• Clearly identifying the usage of the structure, dates of construction, reason behind the fire, the duration of fire and

the extinguisher that was used.

• Revising the design drawings, construction materials used, technical specifications and construction tests data.

• Conducting an investigative field and laboratory inspection on the structural elements.

3

• Conducting engineering analysis on the findings.

• Categorizing the concrete structural damages into different classes and developing conclusions about the current

status of each class, cause and extension of damage.

• Submitting suggestions for the appropriate remedial plan.

Following is an explanation for every part of these steps that were implemented during the project period.

2.1 Onsite Assessment of Reinforced Concrete Condition

According to an American Society for Testing and Materials (ASTM) publication, “Significance of Tests and

Properties of Concrete and Concrete-Making Materials,” concrete appearance after fire damage provides important

insight about the severity of the damage and the estimated temperature the fire reached during the incident. As the

temperature of the fire increases, the color of concrete changes to pink at temperatures between 400-600˚C, a

whitish grey colour at temperatures between 600-900˚C and a buff color when the temperature exceeds 900˚C. This

is usually associated with significant reduction in the compressive strength of the concrete. Reinforcement steel, on

the other hand, shows a deterioration of yield strength and elasticity under fire. While there will not be a significant

variation in the steel yield strength of 420 MPa steel grade up to 500˚C, an unrecoverable reduction of 84% in the

original yield strength will occur after exposure to 800˚C even after bringing the steel temperature back to cool room

temperature (Ilker Bekir Topcu and Cenk Karakurt 2008). Onsite visual, destructive and non-destructive tests, along

with other laboratory tests were completed to evaluate the exact condition of the defective reinforced concrete

elements.

2.1.1 Onsite Visual Inspection

Typically, visual inspection is one of the first steps in the evaluation of a damaged concrete structure, and it can

provide valuable information about the current condition of the structure and the proper corrective actions that

should be taken by knowledgeable and expert investigators. During their frequent visits to the project, ACES

completed a full examination of the affected structural elements and freshly exposed surfaces, inspection and

classification of existing damage and examination of concrete lumps samples. The information obtained from this

comprehensive visual inspection included:

• The type and size of the deterioration (e.g. cracking, concrete spalling, surface deterioration, peeling off, concrete

color, buckling and other).

• The presence of defects or possible defects that need further detailed inspection.

• Whether the defect size is static (i.e. will not change) or dynamic (i.e. might increase or decrease).

All these observations were documented on an appropriately designed checklist and supported by sufficient

photographs from the site. The checklist included data about (a) location of the element, (b) description of the

element, (c) dimensions of the element, (d) concrete cover, (e) depth of carbonation, (f) depth of color change in

concrete, (g) observed color, and (h) details of the damage. The results of the visual examination are shown in Table

(A.1) in Annex A.

2.1.2 Onsite Non-Destructive Tests

Non-destructive testing (NDT) on damaged concrete structures can provide a wealth of information about the

structure’s integrity and adequacy. For severely defected structures, it is common that this kind of testing is used as a

preliminary evaluation tool to a subsequent destructive testing to establish a full and clear image about the concrete’s

status.

According to the International Atomic Energy Agency, Vienna Training Course No.17 “Guidebook on non-

destructive testing of concrete structures,” there are 14 basic methods for NDT of concrete structures. In this project,

three main methods were used to evaluate the condition of the damaged concrete structure which were sounding test,

depth of carbonation and cover of reinforcement.

2.1.2.1 Sounding Test

The sounding test is a simple method used to determine the deterioration of concrete by using a hammer, which

produces a hollow dull thud sound when deteriorated weak material is present. This method needs an expert

investigator who is able to recognize the differences in concrete sounds. It was indicated by this test that the face of

the shear walls at the utility shaft near the front elevators and the shaft near the northern staircase were the most

4

severely affected elements by the fire.

2.1.2.2 Depth of Carbonation

Carbonation of concrete, which is also known as depassivation, occurs when the carbon dioxide reacts with calcium

hydroxide in the cement paste to produce calcium carbonate, which tends to neutralize the concrete (i.e. decrease the

pH value) and thus results in losing the passive protection of the reinforcement steel. This test was critical due to the

large amount of carbon dioxide emissions that resulted from the fire.

The depth of carbonation was measured by applying a solution of phenolphthalein in diluted ethyl alcohol on freshly

exposed concrete surface. The color of this chemical solution changes from colorless to pink when the pH is higher

than 10. Therefore, the depth of the carbonated layer (i.e. depth of the uncolored layer) can be easily determined as

shown in Figure 2.

Figure 2. Depth of carbonation test (Photo credit: ACES)

According to the ACES assessment report, the depth of carbonation was between 0 to 10 mm in columns, 0 to 8 mm

in walls and 2 to 20 mm in slabs and beams. All these depths were measured from the existing surface of concrete

elements and fortunately, the carbonation depth did not extend to the steel bars in all locations.

2.1.2.3 Cover of Reinforcement

The cover of reinforcement was evaluated using covermeter equipment which consisted of a search head, meter and

an interconnecting cable. The concrete surface was scanned with the search head in contact with the surface so that

the meter provided indication about the concrete cover and the location of steel bars. In this project, the cover of

reinforcement was evaluated using a CT-4950A Micro Covermeter.

According to the ACES assessment report, the concrete cover ranged between 30 to 60 mm for columns, 8 to 10 mm

for walls and 25 to 40 mm for beams. These readings were measured from the existing concrete surface.

2.1.3 Onsite Destructive Testing

As mentioned earlier, usually, non-destructive tests represent a preliminary evaluation for a concrete structure prior

to onsite destructive tests that aim to understand concrete behavior under different loads or to identify more details

about the steel reinforcement bars by creating direct concrete openings to inspect the steel’s condition.

2.1.3.1 Direct Concrete Openings

63 concrete openings were carried out on columns, beams, slabs and walls to inspect the condition of the

reinforcement bars and their cohesion with the surrounding concrete and verify the depth of carbonation and the

thickness of concrete cover. Through visual inspection of steel bars after the removal of concrete lumps, the steel

color was found to be normal and was not directly affected by the fire according to the ACES assessment report.

However, it was noted that the color of some of the reinforcement bars in the shear walls changed to black and they

were slightly buckled. To verify the mechanical properties of the steel bars, 27 bars were taken to the ACES

laboratories to be tested.

2.1.3.2 Concrete Core Drilling

73 concrete cores were taken from reinforced concrete columns, beams, slabs and walls using a rotary core cutting

machine with diamond bits. The nominal diameters of these cores were 2, 3 and 4 inches and their length-to-

diameter ratio (l/d) was more than 1. They were divided into two parts: inner and outer cores for those taken from

columns and walls and upper and lower for cores taken from slabs and beams. All the cores were examined visually,

photographed and clearly numbered and described before testing them for specific physical and mechanical

properties. Figure 3 shows concrete coring in one of the columns onsite.

5

Figure 3. Concrete coring in a column onsite (Photo credit: ACES)

2.2 Laboratory Testing

Several laboratory tests were performed at the ACES laboratories on the concrete cores and steel bar samples that

were collected from the site in order to investigate the physical and mechanical properties of the concrete and steel

elements. These tests were in accordance with ASTM standards and Jordanian Standards (JS) and included:

• ASTM C42-12: “Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of

Concrete”

• JS 441:2002: “Steel - Carbon steel bars for concrete reinforcement - Part 1 : Hot rolled grade 300, grade

420, and grade 460, and grade 520 steel bars”

• ASTM A370-03a: “Standard Test Methods and Definitions for Mechanical Testing of Steel Products”

2.2.1: Physical and Mechanical Properties of Concrete Cores

The compressive strength of the samples that were collected by direct concrete coring where tested in accordance

with ASTM C42-12. As mentioned earlier, different core diameters were taken from the site with length-to-diameter

ratios not less than 1.0. Typically, the length-to-diameter ratio should be between 1.9 and 2.1, however, if it is

difficult to obtain cores within this range, the testing method defines correction factors for the compressive strength

of samples that have a length-to-diameter ratio that is less than 1.75.

The density of the concrete cores was evaluated prior to the compressive strength test. The length, diameter and

weight of each core were reported and the density was calculated. According to the ACES report, the average

density of the cores that were taken from columns was 2,324 kg/m3 and the average for the cores taken from slabs

and beams was 2,328 kg/m3, which are accepted as normal weight concrete mix.

The compressive strength of the structure was evaluated by testing the 73 cores that were obtained from columns,

walls, beams and slabs. The results demonstrated notable variations in the structural behavior of the concrete

elements throughout the building. The 2nd

, 3rd

and 7th

floors were the least affected by the fire, as there was a

neglected difference between the residual strength of concrete exposed directly to fire and the original design

strength. On the other hand, the 4th

, 6th

and 10th

floors were the most affected floors with reduction in compressive

strength that exceeded 30% in some locations.

Most importantly, there were notable differences between the two splits of each core (i.e. inner and outer for

columns and upper and lower for beams and slabs) which meant that the structural elements of the building were not

really homogeneous with notable variations ranging between 5% and 33% in some locations as per the ACES report.

The results of the concrete core tests are shown in Table (A.2) in Annex A.

2.2.2 Physical and Mechanical Properties of Steel Reinforcement

As mentioned earlier, the yield strength of reinforcement strength may be permanently affected by extremely high

temperatures. To ensure the integrity of the reinforcement bars, 27 bars of different diameters were taken from the

site and tested in the ACES laboratory in accordance with JS 441:2002 “Steel - Carbon steel bars for concrete

reinforcement - Part 1: Hot rolled grade 300, grade 420, and grade 460, and grade 520 steel bars.” The results

indicated that the steel reinforcement was not affected by the fire. The yield strength ranged from 487 to 718 MPa

while the tensile strength ranged from 635 to 832 MPa. These results exceeded the design yield and tensile strength

of steel bars, which are 420 and 612 MPa respectively. The results of the reinforcement steel bars tests are shown in

6

Table (A.3) in Annex A.

2.3 Recommendations and Conclusion for Repair Approach and Material

In order to establish a systematic and objective approach that evaluates the condition of the structural elements, all

the information gathered by the visual inspection and results obtained through non-destructive and destructive site

testing and laboratory testing were classified in accordance with “Concrete Society Technical Report No. 15,

Assessment of fire damaged concrete structures and repair by gunite.” This report classifies the damaged concrete

and the needed repair method into 4 classes as shown in Table (A.4) in Annex A.

All these tests showed that the fire affected the structural elements of the building but not to the extent that requires

the demolition and reconstruction of any of these elements. In general, the damaged concrete classification of

columns, beams and slabs in the building ranged from Class 1 (i.e. minor deterioration with smoke deposit) to Class

3 (i.e. substantial deterioration with extensive spalling out), while the face of shear walls at the utility shaft near the

front elevators and the shaft near the northern staircase were severely affected by the fire and thus classified as Class

4 (i.e. severe damage with substantial deflection and/or buckling). The carbonation had already taken place but to

depths less than that of the concrete cover and therefore, the carbonation of concrete was not a major concern.

According to the ACES report, there was a notable reduction in the concrete compressive strength in some areas, the

highest reduction in columns’ compressive strength occurred at the 4th

floor which ranged from 17.6-35.9% while

the highest reduction for slabs and beams was at the 6th

floor which ranged from 4.5-36.1% comparing to original

design strength. ACES concluded that the restoration of structurally damaged areas should be done by patching the

defected areas and building up the spalled concrete sections to their original contours and sealing any apparent

cracks. When dealing with minor superficial damage, they recommended only light sandblasting to remove the

smoke damage before the application of the cosmetic repair materials. Where there was very severe damage, ACES

recommended removing all deteriorated concrete, this did not only include spalled and weak concrete but also the

concrete that had changed in color. A summary for all these examinations is shown in Table (A.5) in Annex A.

ACES recommended that the repairing material should be as similar as possible to the host concrete, with

compressive strength not less than the design strength of the original concrete elements which was 30 MPa. Also,

the material should have very low shrinkage properties and match the color and texture of the original surfaces.

Since the defected area was too large, the traditional hand applied repairing mortar would be impractical to restore

the structural integrity. Instead, it was agreed to use a high performance shotcrete material for this job for more

effective repair.

3. Development of the Repair Material

3.1 Types of Shotcrete

According to the “Standard Practice for Shotcrete” published by the US Army Corps of Engineers, there are 4 main

types of shotcrete, which are: (a) Fiber-reinforced shotcrete, (b) Silica-fume shotcrete, (c) Polymer-modified

shotcrete, and (d) Accelerated shotcrete.

Fibers used in shotcrete mainly come in 3 forms that are steel, glass or synthetic fiber made of polypropylene,

polyethylene, rayon and more. Unreinforced shotcrete, just like unreinforced concrete, is a very brittle material that

will show a propagation of cracks when subjected to tensile stresses due to external actions or thermal movements,

therefore introducing certain dosage of fiber to a shotcrete mix will enhance the ductility characteristic of the

shotcrete and make it more able to withstand deformations or control cracks.

Silica fume is super fine non-crystalline material made of silica which is used to significantly increase the strength

of the shotcrete by producing a more dense mix that has better cohesive characteristics and thus reduce the water

permeability of the mixture. Commonly, silica fume shotcrete used in conjunction with fiber yields a higher strength

and lower shrinkage rate mixture.

In some cases, where higher bond, tensile and flexural strengths are required along with having a more waterproof

shotcrete mix, polymer emulation can be used to partially or totally replace the mixing water. This is one of the most

common forms of polymer-modified shotcrete that can be easily done onsite.

Accelerated shotcrete is prepared by introducing accelerating admixtures to the shotcrete mix. These admixtures

may come in liquid or powdered statues for wet or dry process shotcrete. Accelerated shotcrete is commonly used

for high-build thickness work on vertical and overhead applications because it allows for fast section buildup; it is

also used for rapid repair work that needs sufficient early strength values.

7

3.2 Development of the Repairing Product

Properly formulated shotcrete material guarantees the integrity and durability of the repaired sections. The first step

to developing an effective repair product is to understand key aspects of a project that include the ultimate strength

requirement, strength development rate, maximum application thicknesses at vertical and overhead surfaces and the

general site conditions (i.e. exposure to chemicals, weathering conditions, freeze/thaw cycles and more). The repair

products for this project were developed by DCP Jordan, a multi-national construction chemicals company that has

been serving this field for more than 85 years. DCP Jordan understood the exact requirements of the project and

worked on the development of a special dry-mix shotcrete product called Cempatch SD300.

Cempatch SD300 can be classified as a fiber-reinforced and silica fume shotcrete combination that was developed to

satisfy the challenging repair requirements which were mainly high early strength, high ultimate strength and

reduced shrinkage repairing mortar. More specifically, DCP’s Cempatch SD300 is a pre-packaged dry-mix shotcrete

product that was designed to be applied to a maximum thickness of 150 mm in vertical applications and 100 mm in

overhead applications in a single layer. This product suited the site and project requirements as it was reinforced by

certain dosages of polypropylene fibers, and showed a neglected drying shrinkage rate less than 0.3%, as per the

manufacturer’s declaration.

The silica fume content played a significant role in developing the early and ultimate strength of the product. Since

time was a major challenge for all the parties who were working on this project, it was necessary to develop a repair

material that had sufficient early strength so that the contractor can proceed with the other installations as fast as

possible without adversely affecting the quality of the work. The overhead repair works represented the main

challenge for this case since the majority of service, electrical and gas conducts and pipes were to be fixed and hung

on the repaired slabs, and thus adding heavy pulling action on the repaired surfaces. However, due to the high early

strength performance that Cempatch SD300 offered, it was possible to fix these pipes and conducts simultaneously

while doing the repairing work. This early compressive strength that exceeded 20 MPa as per the manufacturer’s

declaration also reflected an exceptional high ultimate strength which exceeded 55 MPa at 28 days, and that was far

beyond the original concrete grade that was 30 MPa.

One of the main considerations that arose after adopting shotcrete as an option for the rehabilitation and repair

works was the quantity of rebound, which is defined as the amount of cement paste and aggregate that bounce off

the surfaces during the shotcrete application. Besides that it depends on the professionalism of the applicator and the

air pressure used for the application, rebound of shotcrete significantly depends also on the composition of the

material itself, mainly, the cement content, water content and, most importantly, the size and gradation of aggregate.

With special water retention additives, and well-graded aggregate content that has a top cut of 3.0 mm size, DCP

Jordan was able to develop a product that met the ACES recommendation for high performance repairing material

and facilitated the application process for B.E.M.C.O Engineering by providing a product that can be applied in a

closed working environment in a safe and easy manner.

By February 2014, DCP Jordan completed all the verifications on the performance of their dry-mix shotcrete repair

mortar and started producing it in their factory in Madaba, Jordan, and transferred it to the site in the form of 25 kg

pre-packaged bags that were ready to use onsite. DCP Jordan was able to deliver around 1,000 Tons of the product

to repair the structurally defective areas within 3 months.

Figure 4. Shotcrete product onsite in preparation for the repair works (Photo credit: B.E.M.C.O Engineering).

8

4. Onsite Application of Shotcrete

The application of shotcrete should be carried out by expert applicators since it involves some hazardous risks that

include the shooting of material, rebound, clogged nozzle or hose, and dusting. The application of the dry-mixed

shotcrete product was entrusted to B.E.M.C.O Engineering, a well-known contracting company in Jordan

established in 1987 and specializes in pre-casting and pre-stressing of bridges and buildings, as well as the

installation of reinforced earth structure, shotcrete, grouting and other civil engineering aspects.

4.1 Surface Preparation

The first step for a successful concrete repairing plan is to remove all unsound material until unaffected sound

concrete is reached. This is done onsite by mechanical chipping of all defective elements. In some cases, columns,

walls and slabs were chipped to a thickness up to 100-120 mm and thus large thicknesses of shotcrete were required

to restore the member to its original structural properties as shown in Figure 5.

Figure 5. Chipping of ribbed slabs and beams (Photo credit: B.E.M.C.O Engineering).

All sound surfaces were treated using sandblasting and grinding of high pressure water jetting then thoroughly

cleaned and soaked with clean water

to reach a saturated surface dry condition prior to applying the shotcrete repairing mortar.

4.2 Placement of Shotcrete

On February 10, 2014, B.E.M.C.O Engineering started with the structural repair work for the project. The beams

and ribs of the 10th

floor were the first structural elements that were repaired. Overhead work repairs were more

challenging as they required more attention on the mixing water flow since an excess of water could lead to

puddling or dropping out of the repairing shotcrete, while insufficient water could increase the rebound and crate

lumps making the finishing more difficult. Figure 6 shows an expert applicator placing shotcrete on an overhead

slab.

Figure 6. Overhead application of shotcrete onsite (Photo credit: B.E.M.C.O Engineering).

The general approach of applying a dry-mix process shotcrete starts with feeding the pre-packaged shotcrete product

through a pre-moisturizer. Moisture content of 3-6% by dry mass improves the cohesiveness between the cement

9

and aggregate but the mixture should not be wetted to an extent that causes a pasty consistency. This mixture is fed

into the gun then introduced into the delivery hose. Compressed air is then added to the gun and the mixture is

carried through the delivery hose to the nozzle where water is introduced from a perforated water ring fitted inside

the nozzle and finally the shotcrete is pushed at high velocity onto the prepared surfaces.

Initially, thin coats of shotcrete were applied to the prepared surfaces. These coats control the rebound especially at

sections with deep and high thicknesses. While still wet, a second layer of shotcrete was applied to the first coat on

the areas where higher thicknesses were needed to restore the original concrete cover and contours.

As mentioned previously, shear walls at the building service shafts were the most affected structural elements from

the fire. This case represented another challenge during the application of shotcrete due to the difficulty in the

accessibility of that area and the high thicknesses that were needed to restore the structural integrity of the shear

walls. As reinforcement bars were significantly exposed at some of those areas, a total of 50 mm thickness was

needed to restore those elements and provide enough concrete cover for the reinforcements.

Figure 7 shows a comparison of elevator walls before and after applying the shotcrete.

Figure 7. Elevator walls before (left) and after (right) the repairing works (Photo credit: B.E.M.C.O Engineering).

Overall, the repair work using shotcrete covered approximately 15,000 m2 of slabs and beams, 1,200 m

2 of columns

and 2,050 m2

of walls and service shafts. All these areas were repaired and finished by expert applicators not only to

restore the structural integrity, but also to achieve the best alignment and develop a smooth finish to facilitate the

electro-mechanical works that followed the repairing work as shown in Figure 8.

Figure 8. Installation of electro-mechanical works after repairing works (Photo credit: B.E.M.C.O Engineering).

4.3 Post-Repairing Testing and Verification

After application, it is important to evaluate the quality of shotcrete following almost the same evaluation tools

mentioned in Section 2. All surfaces should be inspected for soundness and uniformity and to determine if any

cracks, voids, damaged sections or water leakages are taking place on the finished surfaces.

Besides the visual inspection, several destructive tests took place at selective sections to verify the physical and

mechanical properties of the shotcrete. These tests were completed to determine the density and compressive

strength of the shotcrete cores brought to the ACES laboratory from the site, as well as to verify the pull-off

adhesion strength between the shotcrete and concrete substrates as shown in Figure 9. 19 cores of shotcrete were

taken from the site and tested for compressive strength after different periods of time of placement ranging from 3 to

28 days. Since the shotcrete product developed by DCP Jordan had a special formulation to improve the early

strength development, the product exceeded the designed compressive strength of the host concrete which was 30

MPa after 3 days of placement only and achieved more than the double this value at 7 days only when tested as per

10

the British Standard BS EN 12390-3 “Testing hardened concrete. Compressive strength of test specimens.” Besides

the compressive strength, the adhesion to concrete surfaces was tested by pull-out means in accordance with EN

1542 “Products and systems for the protection and repair of concrete structures. Test methods. Measurement of bond

strength by pull-off.” The results demonstrated that the shotcrete had very good adhesion with concrete surfaces as

all the acceptable results showed that the failure pattern was in the concrete surface itself. ACES’s reports for the

onsite testing after shotcrete placement are shown in Annex B.

Figure 9. Post-repairing verification by concrete coring (Photo credit: B.E.M.C.O Engineering)

5. Conclusion

By the beginning of May 2014, after around 90 days of starting the application repairing plan and only 9 months

after the fire, all the structural repairing works at Farah Hospital’s extension building (Kilani Health Care Institute)

were completed and the project was successfully put back onto its track. This project presented an ideal case of an

integrative rehabilitation process between several engineering parties who worked together to complete all the

repairing works at the highest level of quality within an exceptional period of time. The project presented many

challenges due to the extent of the damages the building incurred. ACES was able to provide a comprehensive

assessment of the damages by undertaking various tests onsite and in its laboratories. MPCE used this assessment to

formulate the best repair strategy by working with DCP Jordan and B.E.M.C.O Engineering. DCP Jordan developed

Cempatch SD300, a special pre-bagged dry-mix process shotcrete product that was designed to fulfill the project’s

requirements, and it was applied by B.E.M.C.O Engineering, who completed all the required repair work within 90

days. This project also demonstrated how shotcrete is one of the most effective methods, in terms of cost, quality

and productivity to restore the structural integrity of defective reinforced concrete.

Today, Farah Hospital’s extension building along with the original hospital building are equipped with the latest

medical technology in the field of gynecology and obstetrics that are run by highly qualified staff to make the dream

of thousands of couples having healthy children come true.

Acknowledgment

We would like to thank all those who supported the preparation of this paper with the needed information, reports

and images. Our thanks to Messrs. Farah Hospital represented by Dr. Sanad Kilani, Madi & Partners Consulting

Engineers represented by Dr. Osama Madi, Arab Center for Engineering Studies represented by Dr. Amjad

Barghouthi, DCP Jordan represented by Eng. Laith Qirresh, and B.E.M.C.O Engineering represented by Eng. Omar

Bseiso for the valuable information they shared with us. Special thanks for Miss Aya Aghabi for her assistance in

editing and revising the content of this paper.

References

American Concrete Institute (2010), Field Guide to Concrete Repair Application Procedures - Concrete Repair by

Shotcrete Application, Reported by ACI Committee E706, Farmington Hills, USA.

Arab Center of Engineering Studies (2014), Assessment of Effect of Fire on Concrete Structural Elements for The

Kilani Health Care Institute, Amman, Jordan.

ASTM International (2003), ASTM A370-03a, Standard Test Methods and Definitions for Mechanical Testing of

Steel Products, West Conshohocken, PA, USA.

ASTM International (2012). ASTM C42/42M-12, Standard Test Method for Obtaining and Testing Drilled Cores and

Sawed Beams of Concrete, West Conshohocken, PA, USA.

British Standards Institution (2009), BS EN 12390-3:2009 Testing hardened concrete - Compressive strength of test

11

specimens, London, UK.

British Standards Institution (2008), BS EN 1504-9:2008 Products and systems for the protection and repair of

concrete structures. Definitions, requirements, quality control and evaluation of conformity. General principles

for use of products and systems, London, UK.

British Standards Institution (1999), BS EN 1542:1999, Products and systems for the protection and repair of

concrete structures - Test methods - Measurement of bond strength by pull-off, London, UK.

Concrete Society Working Party (1978), Assessment of fire-damaged concrete structures and repair by gunite, London, UK.

D. Bseiso & Partners Co. (2014), Kilani Health Care Institute Structural Repair Project, Amman, Jordan.

˙Ilker Bekir Topc¸u and Cenk Karakurt, Properties of Reinforced Concrete Steel Rebars Exposed to High

Temperatures. Department of Civil Engineering, Eskis¸ehir Osmangazi University, 26480 Eskis¸ehir, Turkey.

International Atomic Energy Agency (2002), Guidebook on Non-destructive Testing of Concrete Structures, Vienna,

Austria.

Jordan Standards and Metrology Organization (2000), JS 441, Carbon steel bars for concrete reinforcement - Part

1 : Hot rolled grade 300, grade 420, and grade 460, and grade 520 steel bars, Amman, Jordan.

Joseph F. Lamond and James H. Pielert (2006), Significance of Tests and Properties of Concrete and Concrete-

Making Materials, ASTM Stock No.: STP169D, West Conshohocken, PA, USA.

US Army Corps of Engineers (2005), Standard Practice for Shotcrete, Washington DC, USA.

12

Annex. A: Tables

Table (A.1): Sample of Visual Examination and Description of Structural Elements in Accordance with ACES’s

Report

Location Exp. 1 Second Floor

Description Beam soffit in 2nd

Floor Slab

Dimension (mm) 1500 x 320

Plastering thickness (mm) -

Concrete cover (mm) 25

Depth of carbonation (mm) 8

Depth of change in color:

- In Plaster (mm)

- In concrete (mm)

-

9

Observed color Pink

Details of damage and notes: - Concrete surface was spalled up to 20mm over soffit.

- Steel reinforcements were exposed.

- Good bond between steel and concrete.

Location Exp. 8 Second Floor

Description Interior reinforced concrete column






- In Plaster (mm)

- In concrete (mm)

-

0

Observed color Normal

Details of damage and notes: - Concrete surface was good before exposure.


Location Exp. 9 Fourth Floor

Description Interior reinforced concrete circular column

Dimension (mm) -

Plastering thickness (mm) 5




- In Plaster (mm)

- In concrete (mm)

0

15

Observed color Pink

Details of damage and notes: - Loss of plaster, concrete surface having spalling.


Location Exp. 14 Fourth Floor







- In Plaster (mm)

- In concrete (mm)

-

6

Observed color Light Pink

Details of damage and notes: - Micro-cracking of concrete (surface crazing).


13

Description Exterior reinforced concrete column






- In Plaster (mm)

- In concrete (mm)

0

9

Observed color Pink

Details of damage and notes: - Concrete surface having micro-cracking (surface

crazing) and minor spalling along columns edges.


Location Exp. 22 Fifth Floor

Description Wall

Dimension (mm) 200





- In Plaster (mm)

- In concrete (mm)

-

4

Observed color Pink


crazing) and minor spalling along wall edges.



Description Exterior reinforced concrete column

Dimension (mm) -





- In Plaster (mm)

- In concrete (mm)

-

8

Observed color Pink

Details of damage and notes: - Concrete surface having spalling at column.

- Steel reinforcements were exposed at bottom.



Description Beam soffit in 5th

Floor Slab

Dimension (mm) -





- In Plaster (mm)

- In concrete (mm)

0

1


Details of damage and notes: - Concrete surface was good before exposure and only

smoke/soot covered.


Location Exp. 34 Sixth Floor

14


Floor Slab






- In Plaster (mm)

- In concrete (mm)

-

7

Observed color Pink

Details of damage and notes: - Concrete surface was spalled up to 20mm over soffit.

- Steel reinforcements were exposed.


Location Exp. 46 Seventh Floor


Floor Slab






- In Plaster (mm)

- In concrete (mm)

-

3

Observed color Pink

Details of damage and notes: - Micro-cracking of concrete (surface crazing).


Location Exp. 49 Eighth Floor







- In Plaster (mm)

- In concrete (mm)

-

3

Observed color Pink


crazing) and minor spalling along columns edges.


Location Exp. 51 Ninth Floor


Floor Slab






- In Plaster (mm)

- In concrete (mm)

0

7

Observed color Pink


crazing) and minor spalling.


Location Exp. 63 Tenth Floor


Floor Slab


15





- In Plaster (mm)

- In concrete (mm)

0

5


Details of damage and notes: - Concrete surface was good before exposure and only

smoke/soot covered.


16

Table (A.2) Mechanical Properties of Concrete Cores in Accordance with ACES’s Report as per ASTM C42/42M-12

Core No. Location

(a) Core

Strength

(N/mm2)

(b) Correction

Factor

(c) Correction

Core

Strength

(N/mm2)

(d) Estimated

Cube

Strength

(N/mm2)

(e) Reduction

in

Strength

(%)

1 Upper

2nd

Floor Slab 39.03 0.924 36.06 42.92 -

Lower 34.78 0.892 31.01 36.91 -

2 Outer Column in 2

nd

Floor

34.43 0.903 31.10 37.01 -

Inner 41.20 0.915 37.68 44.84 -

3 Upper

2nd

Floor Slab 40.66 0.953 46.75 55.64 -

Lower 29.33 0.947 34.92 41.55 -

4 Upper

2nd

Floor Slab 36.53 0.920 33.61 39.99 -

Lower 23.86 0.945 30.07 35.80 -

5 Upper

2nd

Floor Slab 30.91 0.907 28.03 33.35 -

Lower 28.09 0.873 24.51 29.15 2.8

6 Upper

2nd

Floor Slab 38.42 0.923 35.46 42.20 -

Lower 34.02 0.929 31.62 37.62 -

7 Upper

2nd

Floor Slab 32.24 0.924 29.80 35.46 -

Lower 29.06 0.913 26.53 31.57 -

8 Upper

2nd

Floor Slab 38.34 0.909 36.22 43.11 -

Lower 31.43 0.901 28.33 33.72 -

9 Outer Column in 2

nd

Floor

39.97 0.874 34.93 41.56 -

Inner 34.14 0.935 31.93 38.00 -

1 Upper

3nd

Floor Slab 30.72 0.935 28.73 34.19 -

Lower 28.50 0.940 26.89 32.00 -

2 Upper

3nd

Floor Slab 33.70 0.929 31.30 37.25 -

Lower 36.70 0.931 34.18 40.68 -

3 Upper

3nd

Floor Slab 37.97 0.933 35.43 42.16 -

Lower 35.42 0.956 34.24 40.74 -

4 Upper

3nd

Floor Slab 39.45 0.956 37.72 44.89 -

Lower 32.37 0.969 31.76 37.80 -

5 Outer Column in 3

rd

Floor

32.59 0.888 28.95 34.45 -

Inner 39.30 0.920 36.16 43.03 -

6 Outer Column in 3

rd

Floor

28.78 0.880 25.33 30.14 -

Inner 34.11 0.933 31.84 37.88 -

7 Upper

3nd

Floor Slab 34.39 0.992 34.15 40.64 -

Lower 36.28 0.923 33.47 39.83 -

8 Upper

3nd

Floor Slab 35.01 0.957 33.91 40.35 -

Lower 28.50 0.957 27.28 32.46 -

9 Upper

3nd

Floor Slab 38.12 0.947 37.24 44.32 -

Lower 33.72 0.942 31.76 37.79 -

10 Outer Column in 3

rd

Floor

43.29 0.942 40.77 48.51 -

Inner 44.10 0.950 41.88 49.84 -

1 Outer Column in 4

th

Floor

23.70 0.876 20.76 24.71 17.6

Inner 31.37 0.928 29.11 34.64 -

2 Upper

4th

Floor Slab 31.22 0.899 28.22 34.15 -

Lower 29.54 0.852 25.18 30.47 -

3 Upper

4th

Floor Slab 31.99 0.906 29.43 35.61 -

Lower 28.57 0.902 25.77 31.18 -

4 Upper

4th

Floor Slab 39.68 0.916 36.36 43.27 -

Lower 27.08 0.932 25.91 30.83 -

17

Core No. Location

(a) Core

Strength

(N/mm2)

(b) Correction

Factor

(c) Correction

Core

Strength

(N/mm2)

(d) Estimated

Cube

Strength

(N/mm2)

(e) Reduction

in

Strength

(%)

5 Upper

4th

Floor Slab 39.55 0.901 35.87 40.54 -

Lower 22.81 0.930 21.26 24.03 19.9

6 Outer Column in 4

th

Floor

18.57 0.871 16.19 19.24 35.9

Inner 40.29 0.927 37.34 44.44 -

7 Upper

4th

Floor Slab 37.01 0.872 32.28 39.06 -

Lower 23.13 0.907 21.62 26.16 12.8

8 Upper

4th

Floor Slab 41.84 0.912 38.44 43.43 -

Lower 26.07 0.931 24.48 27.66 7.8

9 Upper

4th

Floor Slab 34.84 0.962 33.64 38.01 -

Lower 32.04 0.911 29.19 32.98 -


th

Floor

37.07 0.872 32.38 38.54 -

Inner 39.81 0.927 36.91 43.92 -

11 Upper

4th

Floor Slab 30.81 0.933 28.74 32.47 -

Lower 28.65 0.871 24.97 28.21 6.0

12 Upper

4th

Floor Slab 27.81 0.939 26.12 29.52 1.6

Lower 22.55 0.938 21.29 24.06 19.8

1 Outer Wall in 5

th

Floor

21.65 0.908 19.66 23.40 22.0

Inner 28.96 0.924 26.74 31.83 -

2 Outer Column in 5

th

Floor

23.34 0.941 21.97 26.14 12.9

Inner 32.19 0.939 30.22 35.96 -

3 Outer Column in 5

th

Floor

35.14 0.908 31.90 37.96 -

Inner 33.76 0.927 31.28 37.22 -

4 Upper

5th

Floor Slab 32.02 0.891 28.53 34.52 -

Lower 27.18 0.896 24.36 29.47 1.8

5 Upper

5th

Floor Slab 33.32 0.896 30.13 36.46 -

Lower 25.85 0.903 23.43 28.35 5.5

6 Upper

5th

Floor Slab 33.62 0.872 29.32 35.48 -

Lower 30.88 0.886 27.36 33.10 -

7 Upper

5th

Floor Slab 40.94 0.889 36.78 44.51 -

Lower 33.40 0.890 29.73 35.97 -

8 Upper

5th

Floor Slab 38.04 0.892 33.94 41.07 -

Lower 34.44 0.911 31.61 38.25 -

9 Upper

5th

Floor Slab 36.81 0.893 32.87 39.77 -

Lower 35.65 0.873 31.51 38.12 -


th

Floor

28.52 0.872 24.86 28.10 6.3

Inner 30.77 0.875 26.92 30.42 -

11 Upper

5th

Floor Slab 31.63 0.900 28.47 32.17 -

Lower 26.69 0.940 27.92 31.55 -

12 Upper

5th

Floor Slab 29.85 0.955 28.49 32.19 -

Lower 30.66 0.941 28.86 32.61 -

1 Outer Column in 6

th

Floor

25.31 0.970 24.56 27.75 7.5

Inner 40.52 0.972 39.37 44.49 -

2 Outer Column in 6

th

Floor

27.35 0.969 26.49 29.94 0.2

Inner 26.69 0.968 25.83 29.18 2.7

3 Outer Column in 6

th

Floor

28.20 0.949 26.75 30.23 -

Inner 39.76 0.943 37.50 42.37 -

4 Upper

6th

Floor Slab 41.60 0.969 40.31 45.55 -

Lower 34.28 0.968 33.50 37.85 -

18

Core No. Location

(a) Core

Strength

(N/mm2)

(b) Correction

Factor

(c) Correction

Core

Strength

(N/mm2)

(d) Estimated

Cube

Strength

(N/mm2)

(e) Reduction

in

Strength

(%)

5 Upper

6th

Floor Slab 26.24 0.966 25.36 28.65 4.5

Lower 21.31 0.938 19.98 22.58 24.7

6 Upper

6th

Floor Slab 23.07 0.968 22.34 25.24 15.9

Lower 17.13 0.970 16.97 19.18 36.1

7 Upper

6th

Floor Slab 23.71 0.972 23.06 26.06 13.1

Lower 24.03 0.934 22.45 25.37 15.4

8 Upper

6th

Floor Slab 26.01 0.972 25.27 28.56 4.8

Lower 28.79 0.970 28.24 31.91 -

9 Upper

6th

Floor Slab 32.93 0.971 31.96 36.12 -

Lower 25.05 0.953 23.87 26.98 10.1

10 Upper

6th

Floor Slab 35.63 0.969 35.49 40.10 -

Lower 32.71 0.970 31.73 35.86 -

11 Upper

6th

Floor Slab 33.27 0.969 32.25 36.44 -

Lower 30.83 0.920 28.37 32.05 -

1 Upper

7th

Floor Slab 27.71 0.873 24.20 29.29 2.4

Lower 30.08 0.891 26.80 32.43 -

2 Upper

7th

Floor Slab 34.18 0.904 31.62 38.26 -

Lower 30.66 0.874 26.79 32.41 -

3 Upper

7th

Floor Slab 33.96 0.895 31.00 37.51 -

Lower 30.25 0.872 26.40 31.94 -

1 Upper

8th

Floor Slab 35.59 0.860 30.61 37.03 -

Lower 28.89 0.913 26.75 32.37 -

2 Upper

8th

Floor Slab 32.08 0.892 28.63 34.64 -

Lower 27.53 0.926 25.82 31.24 -

3 Upper

8th

Floor Slab 23.09 0.900 20.77 25.13 16.2

Lower 24.18 0.914 22.17 26.83 10.6

1 Upper

9th

Floor Slab 31.12 0.903 28.10 34.00 -

Lower 27.74 0.879 24.39 29.51 1.6

2 Upper

9th

Floor Slab 29.43 0.887 26.11 31.59 -

Lower 24.25 0.880 21.35 25.83 13.9

3 Upper

9th

Floor Slab 28.63 0.873 24.99 30.24 -

Lower 18.97 0.921 17.48 21.15 29.5

1 Outer Column in

10th

Floor

19.78 0.916 18.17 20.54 31.5

Inner 31.08 0.905 28.11 31.76 -

2 Outer Column in

10th

Floor

22.54 0.914 20.60 23.28 22.4

Inner 30.41 0.897 27.28 30.82 -

3 Outer Column in

10th

Floor

35.07 0.919 32.23 36.43 -

Inner 37.31 0.936 34.90 39.44 -

4 Outer Column in

10th

Floor

25.57 0.929 23.75 26.83 10.6

Inner 35.97 0.938 33.76 38.15 -

5 Upper

10th

Floor Slab 33.57 0.892 29.96 33.85 -

Lower 35.26 0.889 31.35 35.43 -

6 Upper

10th

Floor Slab 35.07 0.874 30.65 34.64 -

Lower 20.35 0.925 18.82 21.26 29.1

7 Upper

10th

Floor Slab 21.79 0.924 20.14 22.76 24.1

Lower 19.67 0.894 17.82 20.14 32.9

8 Upper

10th

Floor Slab 30.06 0.949 29.07 32.84 -

Lower 22.65 0.930 21.07 23.81 20.6

19

Core No. Location

(a) Core

Strength

(N/mm2)

(b) Correction

Factor

(c) Correction

Core

Strength

(N/mm2)

(d) Estimated

Cube

Strength

(N/mm2)

(e) Reduction

in

Strength

(%)

9 Upper

10th

Floor Slab 27.04 0.914 24.72 27.93 6.9

Lower 28.58 0.904 25.85 29.21 2.6

10 Upper

10th

Floor Slab 30.51 0.890 27.15 30.68 -

Lower 32.99 0.899 29.65 33.51 -

a: Physical strength of the core

b: Correction factor as defined in ASTM C42/42M-12

c: The product of multiplying core strength by the correction factor

d: Equivalent Compressive strength of 150 mm cube

e: Reduction in strength comparing to original design strength (i.e. 30 MPa)

20

Table (A.3): Physical and Mechanical Properties of Reinforcement Steel in Accordance with ACES’s Report as per

JS 441:2000.

Bar

No.

Element

Location

Weight

(gm)

Total

Length

(mm)

Weight

Per

Meter

Run

(Kg/m)

Area

(mm2)

Diameter

(mm)

Yield

Strength

(N/mm2)

Ultimate

Tensile

Strength

(N/mm2)

2nd

Floor

1 Wall 618.9 404.0 1.5 195.2 15.8 487.0 779.0

3rd

Floor

1 Slab 1538.9 401.0 3.8 488.9 24.9 656.0 806.0

2 Wall 644.2 405.0 1.6 202.6 16.1 632.0 715.0

3 Slab 619.0 408.0 1.5 193.3 15.7 572.0 678.0

4th

Floor

1 Wall 629.7 403.0 1.6 199.0 15.9 718.4 812.4

2 Slab 1506.4 399.0 3.8 480.9 24.7 580.5 686.8

3 Slab 473.0 400.0 1.2 150.6 13.8 601.0 675.0

4 Slab 489.0 409.0 1.2 152.3 13.9 662.0 754.0

5 Slab 643.8 411.0 1.6 199.5 15.9 672.0 759.0

6 Slab 648.8 408.0 1.6 202.6 16.1 582.0 664.0

5th

Floor

1 Wall 622.1 3.855 1.5 196.2 15.8 631.1 733.6

2 Slab 511.9 403.0 1.3 161.8 14.4 550.0 635.0

3 Slab 647.0 404.0 1.6 204.0 16.1 607.8 711.7

4 Slab 1002.7 408.0 2.5 313.1 20.0 599.9 750.6

5 Slab 642.7 404.0 1.6 202.7 16.1 573.4 661.2

6th

Floor

1 Slab 611.3 401.0 1.5 194.2 15.7 672.0 762.6

2 Slab 991.3 401.0 2.5 314.9 20.0 618.9 743.4

3 Slab 630.0 406.0 1.6 197.7 15.9 643.5 793.7

4 Slab 626.7 401.0 1.6 199.1 15.9 632.9 766.5

5 Slab 626.7 399.0 1.6 200.1 16.0 582.2 678.7

6 Slab 631.5 404.0 1.6 199.1 15.9 582.6 684.0

7th

Floor

1 Slab 642.5 403.0 1.6 203.1 16.1 589.9 674.1

8th

Floor

1 Slab 625.0 400.0 1.6 199.0 15.9 639.1 796.3

9th

Floor

1 Slab 636.9 405.0 1.6 200.3 16.0 681.9 831.1

10th

Floor

1 Slab 1008.8 407.0 2.5 315.7 20.0 620.7 727.8

2 Slab 976.5 404.0 2.4 307.9 19.8 596.9 751.2

3 Slab 986.0 403.0 2.4 311.7 19.9 693.0 832.3

21

Table (A.4): Assessment of Fire Damaged Concrete Structures and Repair Required in Accordance with Concrete

Society Working Party, Assessment of Fire-Damaged Concrete Structures and Repair by Gunite

Class of damage and therefore

class of repair

Description of Damage

Columns

Class 1 Undamaged except for some peeling of plaster/finish, soot and smoke

deposit.

Class 2 Substantial loss of plaster/finish – concrete surface having extensive micro-

cracking and pink/buff color – minor spalling only.

Class 3 Plaster/finish almost entirely removed; concrete surface buff colored and

elsewhere locally spalled to reveal reinforcement – other areas may have

separation of cover concrete giving "hollow" ring; not more than one main

bar buckled.

Class 4 Severe damage including extensive spalling revealing considerable areas of

steel reinforcement; one or more bars buckled and the column may show

signs of distortion.

Floor Panels

Class 1 Suspended ceiling extensively damaged but some panels may still in place;

a few hollow tiles damaged but reinforced concrete ribs intact except for

smoke/soot; solid RC slab floors smoke/soot covered and only very minor

spalling.

Class 2 Substantial damage to hollow tiles – reinforced concrete ribs spalled with

reinforcement revealed over small areas only. Concrete generally

smoke/soot covered; solid RC slab with spalling revealing not more than

about 10% of area of steel reinforcement – all reinforcement adhering to

concrete.

Class 3 Reinforced concrete ribs (to hollow – tiles floors) extensively spalled but

reinforcement generally still adhering to concrete; concrete soot/smoke

covered or pink; solid RC slabs with spalling revealing over 10% of area of

reinforcement; concrete soot/smoke – covered or pink. No severe deflection.

Class 4 Reinforced concrete ribs (to hollow floors) and solid RC slabs with

considerable amount of reinforcement fallen clear to concrete; deflection

may be substantial.

Beams

Class 1 Soot or smoke deposit; minor spalling only and practically no exposed

reinforcement.

Class 2 Substantial spalling along edges only, revealing main reinforcement (outer

surface of corner bars only) – micro-cracking of surface – cover/concrete to

soffit may have "hollow" ring; concrete color black/pink.

Class 3 Substantial Spalling over soffit/sides revealing reinforcement generally

intact – about 50% perimeter of exposed main bars still in contact with

concrete; not more than one main bar buckled; concrete color buff; cracks

several millimeters in width may exit; no several deflection

Class 4 Severe damage including extensive spalling to soffit/sides revealing

practically all of the lower main bars; substantial deflection and/or fractures

– several main reinforcing bars may be buckled; concrete buff/gray.

22

Table (A.5): Summary of Concrete Cores Test Results in Accordance with ACES’s Report

Location

Structural

Element

Min

(N/mm2)

Max

(N/mm2)

Average

(N/mm2)

Reduction

in

Strength

(%)*

2nd

Floor

Beams

& slabs

Upper 33.35 55.64 41.81 15

Lower 29.15 41.55 35.19

Columns Outer 37.01 41.56 39.29

4 Inner 38.00 44.84 41.42

3rd

Floor

Beams

& slabs

Upper 34.19 44.89 40.54 8

Lower 32.00 40.74 37.33

Columns Outer 30.14 48.51 37.70

14 Inner 37.88 49.84 43.58

4th

Floor

Beams

& slabs

Upper 29.52 43.43 37.34 23

Lower 24.03 32.98 28.40

Columns Outer 19.24 38.54 27.50

33 Inner 34.64 44.44 41.00

5th

Floor

Beams

& slabs

Upper 32.17 44.51 37.45 8

Lower 28.35 44.51 34.21

Columns Outer 23.40 37.96 28.90

15 Inner 30.42 37.22 33.86

6th

Floor

Beams

& slabs

Upper 25.24 45.55 33.34 13

Lower 19.18 37.85 28.97

Columns Outer 27.75 30.23 29.31

21 Inner 29.18 44.49 38.68

7th

Floor Beams

& slabs

Upper 29.29 38.26 35.02 6

Lower 31.94 32.43 32.26

8th

Floor Beams

& slabs

Upper 25.13 37.03 32.27 5

Lower 26.83 32.37 30.15

9th

Floor Beams

& slabs

Upper 30.24 34.00 31.94 20

Lower 21.15 29.51 25.50

10th

Floor

Beams

& slabs

Upper 22.76 34.64 30.45 10

Lower 20.14 35.43 27.23

Columns Outer 20.54 36.43 26.77

24 Inner 30.82 39.44 35.04

* Compared for the same core (inner versus outer in columns and lower versus upper in beams and slabs).

23

Annex B. Sample of Post-Repairing Testing Reports

application of shotcrete in concrete rehabilitation and ... · application of shotcrete in concrete...

Documents